The present invention relates generally to fittings and containers for maintaining fluid under pressure, and, more particularly, to sewage ejector basins or sump arrangements that must be capable of maintaining fluid under pressure therein for a period of time.
Various prior devices are known which are required to receive and retain therein for a period of time fluid which is under pressure. One such type of device is a sewage ejector basin or sump arrangement. Such sump arrangements will typically have an open topped sump container and a submersible electric pump or similar device mounted within it to remove fluid that accumulates in the sump container. Usually, it is desirable to seal the pump within the sewage or sump container by a cover and prevent fluid leakage out of the container through the cover. At the same time, it is often necessary for the pump to have access to a source of electric power via a power cord passing through an opening in the cover.
In order to satisfy certain reliability standards (such as with respect to downstream blockage) for some sump applications, an example being the ten foot stack test widely used in the sewage industry, the seals employed by the cover, particularly those about the power cord opening, must prevent leakage under significantly greater fluid pressure than the sump arrangement is subjected to under conditions of normal use. At the same time, the seals must not crimp the power cord or make the power cord unduly difficult to insert through the cover.
Previously, steel or other metals have been used for the sump container and/or cover. Such metal covers have, for example, been sufficiently rigid as to minimize cover flexing when subjected to higher fluid pressures. Minimizing the flexing of the cover tends to impose less stress on the cover seals and reduce any tendency of the cover seals to leak. With metal covers used in applications requiring sealing against higher pressures, the opening for the power cord has been sealed by an inwardly tapered, elastomeric grommet that can be secured in place by pounding it into the power cord opening to form an interference fit directly or with the aid of gasket tape. However, metal covers tend to be more expensive to manufacture, heavier to transport and more cumbersome to install *than is otherwise desired. Further, metal covers are susceptible to corrosion, especially in certain fluid environments where sump and sewage arrangements have been employed.
It has been suggested to form the sump container and/or the cover from plastic materials, such as polyethylene structural foam, so as to reduce manufacturing costs and weight and simplify installation. However, under higher fluid pressures, such plastic covers have a greater tendency to flex or bulge outwardly. That flexing tends to weaken the interference fit seal and permit leaks past the inwardly tapered, elastomeric grommet in the power cord opening.
In addition, some prior power cord grommets have been molded to have an hole to receive the power cord and a molded slot or groove to allow the power cord to be pushed into that hole from the side of the grommet. After the cord was inserted into the grommet, the grommet would be inserted into the power cord opening of the cover. Under normal conditions of use, the elasticity of the material used to form the grommet, such as flexible PVC, was such that upon compression of the grommet to form the interference fit, the slot was closed and prevented fluid flow therethrough. However, it has been found that in higher pressure applications that compression was insufficient to maintain the seal in the slot, and fluid could leak through the slot.
Accordingly, it is an object of the present invention to provide improved sewage and sump arrangements. Other objects include the provision of an improved sealing grommet for sump covers that:
a. Is inexpensive to manufacture and easy to install,
b. Reliably seals against fluid flow past the power cord over a wide range of fluid pressures, even where the cover experiences flexing under the fluid pressure,
c. Is usable in a wide variety of applications and with both metal and plastic covers,
d. Provides a more secure seal at higher pressures, and
e. Is durable, readily removable and reusable.
These and other objects of the present invention are attained by the provision of a power cord grommet having a compressible, reverse tapered portion that is insertable into *the power cord opening of a sewage or sump basin cover and expandable therein when subjected to higher fluid pressures from within the sump basin so as to form a tighter seal against that opening. That expandability under higher fluid pressure is facilitated by a plurality of tapered recesses in the bottom surface of the grommet adjacent the reverse tapered portion. One or more holes can provided in the grommet to receive the power cord, and a slit is cut from each such hole to the side of the grommet to allow the cord(s) to be inserted into the hole(s).
Other objects, advantages and novel features of the present invention will be readily apparent from the following drawings and description of preferred embodiments.